Method of coating ferrous metals with aluminum



Feb. 14, 1950 c. G. FINK 2,497,119

' METHOD OF COATING FERROUS METALS wm: ALUMINUM Filed Spt. 18, 1944'HYDROGEN ROGEN I 24 2 E 12 g I 1 F A/ H z INVENTOR.

COL/N c1. F/NK BY Patented Feb. 14, 1950 UNITED STATES PATENT OFFICEColin G. Fink, New York, N. Y., assig'nor to Alwac Company, Inc.,Wilmington, Del., a corporation of Delaware Application September 18,1944, Serial No. 554,621

1 Claim.

This invention relates to methods of coating metals with aluminum, orother metals, by immersion in molten baths of the coating metal, andprovides improvements therein.

Metals in continuous forms (wire, strips, sheets, etc.) have beensuccessfully coated on a commercial scale with aluminum, and also withother metals, by suitable pre-treatments. But previous methods have notbeen altogether satisfactory for coating articles such as castings,-

stampings and forgings. The present invention provides a successful andsatisfactory method for coating such types of articles with othermetals, especially with aluminum.

In my Patent #2,082,622, dated June 1, 1937, it has been disclosed thatarticles may be coated with aluminum by pre-packing with hydrogen; Amore simple method for coating articles like castings and the like hasbeen sought. Such a method has been discovered, and is set forth herein.

According to the present invention, articles are immersed or dipped in amolten bath of the coating metal, at ordinary coating temperatures,through which hydrogen is constantly bubbled, and the super-saturationof the bath with hydrogen brings about an adherent coating of thecoating metal on the basis metal which is to be coated.

Having discovered the satisfactory working of the invention witharticles such as castings, it has been further discovered that themethod of the present invention works equally well in coating basismetals in continuous form, such as wire, strips and sheets.

An apparatus suitable for use with the present method is shown in theaccompanying drawing, which is a vertical cross-sectional view.

An example of coating iron and steel castings with aluminum is asfollows:

Aluminum is melted in a suitable pot, such as the pot l9 illustrated.Aluminum melts at about 660 0., and the aluminum bath is ordinarilymaintained at a temperature of 50 to 100 degrees above its meltingpoint. Hydrogen is constantly introduced into the mass of the moltenaluminum, pipes -or tuyeres l2 discharging into the body of the moltenaluminum below its surface being used for introducingthe hydrogen, thelatter super-saturating the molten aluminum, bubbling through it, andescaping at the surface. A hood I! with an ofltake I1 is advantageouslyprovided over the pot It. A trap-door 20 is provided for giving accessto the molten aluminum. Castings are wired. or put into a ladle orbasket, and immersed in the molten aluminum. The castings may be movedabout in the bath (stirring action) to advantage. Before immersion, ahoe is used to remove or skim any dress from a portion of the surface ofthe molten aluminum through which the castings are to be introduced intothe bath. The time of immersion will depend on the mass of the castings.Sufllcient time is allowed for a thin alloy of the basis metal and ofthe aluminum to form, which is from less than one minute to severalminutes. Upon removal, the castings carry with them an adherent coatingof aluminum.

To coat basis metals in continuous form, wire, for example, the wire ispassed continuously into the pot l0 through an orifice 22 which opensinwardly below the surface of the molten aluminum, and the wire may passout of the bath through a similar exit orifice H.

No special pre-treatment of the basis metal is required. Cleaning in c:cordance with good practice to prevent foulin: of the bath and toremove scale, dirt, oil-fllms, etc. is recommended in most cases.

Examples of other coating metals are, zinc,

' cadmium, tin, lead, bismuth, antimony, magnesium, indium, barium andstrontium; and examples of other basis metals are stainless steel,nickel, copper, molybdenum, and tungsten.

What is claimed is:

A method of coating basis metals, comprising continuously introducingstreams or jets of hydrogen below the surface of a molten bath ofaluminum, in quantity in substantial excess of the quantity capable ofbeing absorbed by the molten aluminum, and maintaining said quantity, sothat there is always a surplus of hydrogen in the bath, and immersingferrous basis metal in an ordinary state, capable of absorbing hydrogenfrom the molten bath, in the molten bath of aluminum containing saidexcess of hydrogen.

COLIN G. PINK.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 825,219 Hyde July 3,19082,082,622 Fink June 1, 1937 2,243,979 Reynolds June 3, 1941 2,294,750Harris Sept. 1, 1942

